The objective of this proposal is to develop nanoparticle-based vaccines against West Nile virus. West Nile virus is an emerging human pathogen and a model for other medically important flaviviruses such as dengue virus. We and others have shown that a recombinant subunit vaccine consisting of a truncated form of the flaviviral envelope protein can protect animals from otherwise lethal viral challenges. Here we propose to encapsulate recombinant envelope proteins in biodegradable nanoparticulate cores fabricated from poly(lactic-co-glycolic acid) (PLGA) which have been modified to incorporate immune modulators. Our hypothesis is that this formulation will overcome many weaknesses found in traditional approaches to recombinant subunit vaccine development. First, the formulated antigen is expected to be stable at room temperature for extended periods of time. Second, vaccination can occur with a needle-free procedure (oral or intranasal administration). Finally, our results have shown that immunization with PLGA particles elicits a strong cellular immune response, an essential mechanism to fully eliminate infectious virus. We will synthesize PLGA particles including the envelope protein from West Nile virus. The PLGA particles will include varying concentrations of CpG oligonucleotides as an adjuvant. We will then immunize mice, subcutaneously, orally, and intranasally, with the PLGA preparations. We will vary the number of immunizations and the dose of vaccine administered. The immune response will be characterized in detail. In particular, we will monitor the appearance of virus-neutralizing antibodies as well as virus-specific T cells. We will verify that the immunization is also effective in a distinct strain of mice. Furthermore, we will evaluate the stability of the nanoparticles during storage. Finally, mice immunized with our vaccine against West Nile virus will be challenged with an otherwise lethal dose of live virus. We expect to find that vaccinated animals now survive such a challenge. PUBLIC HEALTH RELEVANCE: Flaviviruses such as West Nile virus and dengue virus cause significant human disease and death. We propose to develop a vaccine against diseases caused by these viruses. The vaccine antigen would be a recombinant protein derived from the viral envelope, and would be encapsulated in nanoparticles. This would allow us to administer the vaccine orally or intranasally.